Chlorine-substituted diarylalkanes as hydraulic fluids



Dec. 6, 1966 E. s. BLAKE ETAL 3,290,253

CHLORINE-SUBSTITUTED DIARYLALKANES AS HYDRAULIC FLUIDS Filed 0G12. 2l, 1955 Fig-l (5 3,290,253 Patented Dec. 6, 1966 3,290,253 CHLORINE-SUBSTITUTED DIARYLALKANES AS HYDRAULIC FLUIDS Edward S. Blake, Ralph E. De Brunner, 4and George A.

Richardson, Dayton, Ohio, assignors to Monsanto Research Corporation, St. Louis, Mo., a corporation of Delaware Filed Oct. 21, 1963, Ser. No. 317,734 16 Claims. (Cl. 252-78) This invention relates to hydraulic systems and more particularly provide-s a hydraulic pressure device comprising an improved operative fluid. The invention also provides some new and valuable hydraulic uids.

The operation lof hydraulic mechanisms generally requires a combination of properties which most liquids do not possess. This is particularly true when the hydraulic system is designed for use in Widely dilfering envir-onments. The hydraulic fluid must often remain liquid over wide temperature ranges, eg., at temperatures which may be below, say, -40 F. and above, say, 400 F. In many applications, fire-resistance of the fluid is of great concern; and, of course, the fluid should not ignite spontaneously at the opening temperature. In numerous applications, it is important htat the hydraulic fluid resist attack by water and/ or oxygen and that it be non-corrosive to the mechanical components with which it may come into contact.

The many rigorous requirements have resulted in the provision of numerous specialty compositions whereby, much as in the lubricant and motor fuel arts, ladditives of various kinds have been admixed with the base iluid for the purpose of imparting to it one or more of the properties in which the base stock is delicient. However, properties such as thermal stability and resistance to hydrolysis generally cannot 'be conferred upon a iiuid by the use of an additive; and although fire-retardant additives for fluids are known, often such additives are of -little value.

Now We have found that certain nuclearly chlorinated diarylalkanes are very useful as operative fluids for hydraulic systems in that they simultaneously possess high thermal stability, are fire-retardant, and resist hydrolysis. The present invention thus provides a hydraulic pressure device and method wherein a displacing for-ce is transmitted to a displaceable member by means of a hydraulic fluid having kinematic viscosity at 25 F. of from 50 to 15,000 centistokes and comprising essentially a chlorine-substituted diarylalkane of the formula R... Z- Rf..

Gly Cla wherein Z is an alkylene radical having from 3 to 10 carbon atoms in the chain which bridges the two benzene rings and a total of from 3 to 12 carbon atoms; R and R are alkyl radicals of from 1 to 4 carbon atoms; the total number carbon atoms in -Z |and Rm-l-R'n is 3 to 16, m and n are numbers of to 3; y is a number of from 1 to S-m, z is a number from 0 to S-n; and the sum of y-l-z is Iat least one-third of, but not more than the total number of aliphatic carbon |atoms present in the molecule.

The presently useful hydraulic fluids comprise a limited. class of nuclearly Ychlorinated diarylalkanes. The aryl group may be phenyl or any alkyl-substituted phenyl having one or more lower alkyl radicals, but having sites available for nuclear chlorination, eg., it may be tolyl, xylyl, mesityl, ethylphenyl, cumyl, diethylphenyl, or tertbutylphenyl. The alkylene portion of the molecule consists of a chain of from 3 to 10 atoms bridging the two benzene rings. The chain may or may not be branched,

i.e., there may be one or more alkyl radicals attached to one or more carbon atoms of the alkylene chain, so long as the total number of carbon atoms in the alkylene group is not greater than 12. The number of chlorine atoms present at the |aromatic nucleus or nuclei is a function of the number of aliphatic carbon atoms present in the molecule, i.e., those present in the alkylene lgroup and in any alkyl substituent in the benzene ring or rings. There should not be present more chlorine atoms in the entire molecule than there are carbon atoms in such aliphatic portions of the molecule, and the least number of chlorine atoms that must be present in onethird of the total number of said aliphatic carbons. For example in 1,3-diphenylpropane, there may be present from l to 3 nuclear chlorine atoms, whereas in an alkylsubstituted 1,3-diphenylpropane Isuch as 1,3-di-o-tolylpropane there may be present a total of from 2 to 5 chlorine atoms as nuclear substituents. The number of chlorine atoms is limited by the sites available for nuclear substitution, i.e., when the benzene rings are unsubstituted a `maximum of l0 sites are available for nuclear chlorination. Hence, even though there may be present as many as l2 carbon atoms in the alkylene portion of the molecule the maximum number of chlorine substituents present in a nuclearly chlorine-substituted diphenyldodecane is 10. Also, when the benzene ring contains alkyl substituents, the number of sites for nuclear chlorination is correspondingly decreased. Thus, although 1,4-diphenyldecane may contain a maximum of 10 chlorine atoms, the nuclearly substituted l,4bis(2,5diethyl pfhenyDdecane which contains more aliphatic carbon can have a maximum of only 6 chlorine atoms since otherwise available nuclear sites are taken up by the four ethyl substituents. There are thus two limitations on the maximum chlorine content: (l) the available sites at the two benzene rings and (2) the number of carbon atoms in aliphatic portions of the molecule. Obviously insofar as the highly aliphatic diarylalkanes are concerned, the number of nuclear sites dictates the maximum of chlorine. However, in compounds having a comparatively low aliphatic carbon content, eg., diphenylnonane and the lower diphenylalkanes, the number of aliphatic carbon atoms is controlling. For example, the maximum amount of chlorine atoms in the presently useful chlorine-substituted diphenylhexanes is 6, even though 10 unsubstituted nuclear carbon atoms are available for chlorination. This maximum, however, will also be reduced in the case of the bis(trialkylphenyl)hexanes, since here again there are available a smaller number of nuclear chlorination sites than there are carbon atoms present in the aliphatic portion of the molecule.

The relationship of chlorine-content t-o aliphatic carbon in the diarylalkanes is important with respect to both viscosity characteristics and to fire-retardant properties of the nuclearly chlorinated diarylalkanes. Although fire-retardant properties generally increase with increasing chlorine-content of a molecule, for the present purpose, in the series of chlorine-substituted diarylalkanes, improvement of fire-retardancy is balanced with viscosity properties. As the chlorine content increases beyond the above-mentioned 1:1 ratio of chlorine atoms to aliphatic carbon atoms, the chlorine-substituted diarylalkanes tend to be solids. Extensive alkyl substitution on the benzene rings is generally inadvisable because presence of the alkyl groups reduces the number of sites available for chlorination.

The presently useful nuclearly chlorine-substituted diarylalkanes are readily available by a number of different processes; e.g., they may be prepared by reaction of the diarylalkane with elemental chlorine under conditions which favor nuclear substitution, by reduction of a bis(chlorobenzoyl)alkane, etc. Of commercial importance is the selective, nuclear chlorination of the diarylalkane, since the reaction is readily effected and requires no diiliculty available starting materials. Generally, the reaction product is a mixture of isomeric chlorine-substituted arylalkanes, i.e., chlorination of a. diphenylalkane will proceed by substitution in the para-, orthoand meta-positions. Also, the reaction product is a mixture of compounds having various degrees of chlorine substitution. Thus, even though there has been employed only suflcient chlorine to give a trichlorinated diarylalkane, the product will contain, in addition to the trichlorinated compound, some higher substitution products, e.g., some tetra, pentaand even hexa-chlorinated material. There will also be present some dichlorinated material to compensate for such higher chlorinated product, so that the average amount of chlorine atoms present in the total reaction product is three, i.e., there are present an average of three atoms of chlorine per molecule of the diarylalkane. We have found that for hydraulic fluid utility it is unnecessary that the chlorinesubstituted diarylalkane be a single compound; rather, what is important for the present purpose is that the fluid chlorination product contain a certain average number of chlorine atoms, which average is at least One-third of the aliphatic carbon atoms present in the molecule. Accordingly, a mixture of chlorinated products is satisfactory for the present purpose, although any individual, normally liquid chlorination product having a chlorine content within the above-described range is useful. The use of the mixture of chl-orination products is primarily an economic expedient since it obviates need of tedious separation. Generally, it will be found that the viscosity characteristics of a mixture consisting, say, of diphenylalkane having a para-chlorine substituent and another compound of better Viscosity characteristics, say, its ortho-chlorine substituted isomer will be a fluid possessing viscosity characteristics which `represent an average of those of the two isomers. Hence mixtures of chlorinated products obtained by elemental chlorination of the diarylalkanes are eminently suited for the present purpose.

Nuclear chlorination of the diarylalkanes is conducted generally by simply passing gaseous chlorine into the diarylalkane, or a mixture thereof under conditions which are known to lead to aromatic, rather than aliphatic substitution. Such conditions usually involve the presence of a chlorine carrier such as iron or iodine or an acidic salt, and exclusion of light. Particularly valuable catalysts for nuclear halogenation are acidic metal salts, e.g., ferrie chloride, aluminum chloride, tin chloride, titanium chloride, etc. The chlorination reaction is generally exothemic; hence application of heat is not required. In some instances, depending upon the nature of the individual diarylalkane and the rate of chlorine input, it is desirable to employ external cooling in order to obtain smooth reaction. An extraneous, inert solvent or diluent may also be employed, but since the diarylalkanes are generally liquids and because the reaction can be easily controlled by regulating chlorine input and/or cooling, the use of extraneous material for this purpose is usually a disadvantage, since such a procedure will generally require removal of the diluent prior to use of the chlorinated product as a hydraulic. fluid. However, if desired, inert diluents such as carbon tetrachloride, chloroform or ether may be used in the reaction.

The point at which chlorination is stopped will be dictated `by the properties desired in the final product. Generally, the extent of chlorination can be gauged by simply noting the chlorine input and change in viscosity of the reaction mixture. In experimental runs, it is recommended that samples of the mixture be taken at intervals and the refractive indices and/or chlorine content determined. Reaction mixtures having an average number of chlorine atoms which is less than one-third of the aliphatic carbon are inadequate hydraulic fluids from the standpoint of fire-resistance and those having an average nurnber of chlorine atoms which is greater than the number of aliphatic carbon atoms are inadequate owing to viscosity characteristics. Therefore, in experimental runs, in order to assure the substantial absence of unsuitable chlorination products or of any reacted material, it is advantageous to distill the crude mixture to obtain a distillation fraction which possesses the desired characteristics.

As herein stated, the invention is of particular economic importance when mixtures of nuclearly chlorine-substituted diarylalkanes obtained by reaction of chlorine with the diarylalkanes are used as the hydraulic fluids, e.g., there may thus be employed the product obtained by nuclear chlorination of 1,3-diphenylpropane to give an average of from l to 3 chlorine atoms per molecule; that obtained by chlorination of 1,4-diphenylbutane to .an average of from 1.33 to 4 chlorine atoms per molecule; that obtained from 1,5-diphenylpentane to give an average of from 1.66 to 5 chlorine atoms per molecule; that obtained from 1,6-diphenylhexane to give an average of from 2 to 6 chlorine atoms per molecule; that obtained from 1,7diphenylheptane to give an average of 2.33 to 7 chlorine atoms per molecule; that obtained from 1,8-diphenyl0ctane to give an average of from 2.66 to 8 chlorine atoms per molecule; that -obtained from 1,9-diphenylnonane to give an average of from 3 to 9 chlorine atoms per molecule; that obtained from 1,10-diphenyldecane to give an average of from 3.33 to 10 chlorine atoms per molecule, etc.

Examples of hydraulic fluids of very good efficacy which are obtained from the branched diarylalkanes are the mixtures of chlorine-substituted products obtained by nuclear chlorination of 1,3-diphenyl-3-methylpropane to give an average of from 1.33 to 4 chlorine atoms per molecule, the product obtained from 1,4-diphenyl-1,3-dimethylbutane to give an average of from 2 to 6 chlorine atoms per molecule; that obtained from 3,3-dimethyl-l,5-diphenylpentane to give an average of from 2.33 to 7 chlorine atoms per molecule; that obtained from 1,6-diphenyl-3-isopropylhexane to give an average of from 3 to 9 chlorine atoms per molecule; that obtained from 3,3- dimethy-1,7diphenylheptane to give an average of from 3 to 9 chlorine atoms per molecule; that obtained from 1,1-dimethyl-1,S-diphenyloctane to give an average of from 3.33 to 10 chlorine atoms per molecule; that obtained from l,7diphenyl-4-tert-butylheptane to give an average of from 3.66 to 10 chlorine atoms per molecule; that obtained from 1,lO-diphenyl-1,10-dimethyldecane having an average of 4 to 10 chlorine atoms per molecule, etc.

As hereinbefore stated when alkyl substitution is present at one or more of the benzene rings of the diphenylalkane, the number of available nuclear chlorination sites is thereby limited. At the same time the increased aliphatic content requires a higher degree of chlorination than is required of the corresponding unsubstituted diphenylalk-ane for obtaining the same fire-retardant properties. For example, whereas the chlorination product of 1,6-diphenylhexane having an average of 2 moles ofv chlorine is a presently useful fluid from the standpoint of both flre-retardance and pour point, a similarly useful fluid cannot be obtained by introducing an average of 2 atoms of chlorine into 1,6-bis(p-isopropylphenyl)hexane. In the latter case, an average of at least 4 atoms of chlorine per molecule must be present. Moreover, although 1,6-diphenyldecane may have introduced into it as many as l0 chlorine atoms in order to obtain outstanding fireresistance 1,6-bis(p-isopropylphenyl)decane may be chlorinated to give a product having at most only 8' chlorine atoms per molecule. To obtain optimum fireretardancy, the simultaneous decrease of available chlorination sites and increase in required chlorination thus limits the aliphatic content of the molecule. Since the number of chlorine atoms which must be present is at least one-third of the number of aliphatic carbon atoms, the

presence of nuclear alkyl substitution must generally be compensated for by decrease in the carbon content of the alkylene portion of the molecule. For example, when the alkylene portion contains the maximum of 12 carbon atoms, there should be present at least 4 chlorine atoms. Addition of three methyl `groups at each of the benzene rings, with an increase of total aliphatic carbon content to 18, requires that there be present at least 6 chlorine atoms in the molecule in order to obtain a product of suitable properties. But since presence ofthe three methyl groups permit a maximum of only 2 chlorine atoms at each benzene ring, it is obvious that a bis (trimethylphenyl)alkane having 12 carbon atoms in the alkane does not serve as a presently useful diarylalkane. On the other hand, a bis(trimethylphenyl)alkane having, say, only, six carbon atoms in the alkane portion, say, 1,6-bis(mesityl) hexane, if completely chlorinated at the two benzene rings :gives a presently useful fluid.

In selecting a suihtable nuclearly alkyl-substituted diphenylalkane, there should also be considered the economics of complete nuclear chlorination. Generally mixtures of products of varying degree of chlorination are much more industrially feasible. Hence starting-matelrials which need not be completely chlorinated to give the required minimum ratio of chlorine to aliphatic content are more desirable. Within the series of ,w-bis- (alkylphenyl)alkanes, for example, the following give chlorination products having the indicated ranges of average chlorine content per molecule:

Starting material: Average No. of Cl atoms 1,6bis(ptolyl)hexane 2.66 to 8 1,5-bis (p-ethylphenyl)pentane 3.0 to 8 1,4-bis(xylyl)butane 2.66 to 6 1,3bis(ptertbutylphenyl) propane 3.66 to 8 1,3-bis(trimethylphenyl) propane 3.0 to 4 1,10-bis(mtolyl)decane 4.0 to 8 1,8-bis(pcumyl)octane 4.66 to 8 l-(ethylphenyl)-6-p-tolylnonane 4.0 to 8 3-ethyll,5bis(xylyl)pentane 3.66 to 6 2-butyl-l,3bis(butylphenyl)propane 5.0 to 8 l-(butylphenyl) -4- (2-ethyl-3 -methylphenyl) butane 3.66 to 7 1,7-bis(2,3-diethylphenyl)heptane 5.0 to 6 S-isopropyl-l,9-bis(p*tolyl)nonane 4.66 to 8 It will be obvious to those skilled in the art that numerous other bis(alkylphenyl)alkanes are suitable starting materials for the production of mixtures of nuclearly chlorinated products having an average number of chlorine atoms per molecule which is at least one-third of, but not more than equal to, the number of aliphatic carbon atoms present in the molecule.

Although for most purposes, mixtures of chlorination products such as those mentioned above are most practical for hydraulic fluid utility, for specialty uses, the individual nuclearly chlorinesubstituted diarylalkanes may be preferred. These may be separated from the mixtures by isolating procedures wel-l known to the art, e.g., by fractional distillation or crystallization, solvent extraction, etc. The individual compounds are also available by employing an indirect method for their preparation rather than elemental chlorination, for example, by reduction of (chloroaroyl)alkanes. One of such individual nuclearly chlorine-substituted diarylalkanes may be employed as the lluid, or two or more may be mixed together to give a compounded lluid having an average of the properties possessed by each.

Individual compounds or mixtures thereof which are employed as hydraulic fluids `according to the invention include, e.g., the chlorine-substituted diphenylalkanes such as 1-(2- or 3-chlorophenyl)-3-phenylpropane, 1,3bis(2 or 3-chlorophenyl) propane, 1,4-bis(2, 3- or 4-chlorophenyl)butane, 1,4-bis(2,3-dichlorophenyl)butane,

1-(2,3dichloro)4( 3chlorophenyl)butane, 1,4-bis 2- or 3 -chlorophenyl -3-methylbutane, 1,4-bis( 3,4-dichlorophenyl)-4-butylnonane, 1,5-bis(2, 3- or 4-chloropheny1) pentane, 1,5 -bis(2,3-dichlorophenyl)-3ethylpentane, 1( 2,3dichlorophenyl)-5 -(3chlorophenyl)3 -methylpentane, 1,6bis(2, 3- or 4-chlorophenyl)hexane, 1-( 3-chlorophenyl) -6(2,3-dichlorophenyl)hexane, 1,6-bis (2,3-dichlorophenyl)hexane, 1,6-bis 2, 3,5 -trichlorophenyl -2-methylhexane, 1,7-bis(2,3-dichlorophenyl)heptane, 1,7-bis (2,3,4-trichlorophenyl)-4-isopropy1heptane, 1, 8-bis (tetrachlorophenyl) octane, 1,9-bis(2,3-dichlorophenyl)nonane, 1,10-bis(2,3,4-trichlorophenyl)decane, l-(pentachlorophenyl -6- (2, 3-dichlorophenyl) decane, 1, l0-bis (pentachlorophenyl decane, 1,7-bis (2,3,4-trichlorophenyl -4-methylheptane, 1,9-bis 2, 3,4-trichlorophenyl) -S-tert-butylnonane, etc.

In the above compounds, the phenyl group may also be substituted with alkyl radicals to the extent that the total number of aliphatic carbon atoms is equal to but not more than three times the number of chlorine atoms present `in the molecule, e.g., the hydraulic iluid may consist of the following individual compounds or mixtures thereof:

1,4-bis 2,3dichloro-4-tert-butylphenyl) butane,

1,5 -bis 3,4-dichloro-2-ethylphenyl -3methylpentane,

1,6-bis 2,5 -dichloro-3,4-diethylphenyl hexane,

1,4-bis 2,3-dichloro-3,4,5-trimethylphenyl) butane,

1,8-bis (2,3-dichloro-4-p-tolyl) octane,

1,9-bis 2,3 ,5-trichloro-4-propylphenyl) -5methylnonane,

etc.

Evaluation of the hydraulic lluid efficacy of the nuclearly chlorine-substituted diarylalkanes was conducted by determining such characteristics as pour point, kinematic viscosity, ASTM slope, autogenous ignition temperature and behavior upon sudden exposure to very high temperatures. The following procedures were used to obtain the data given in the following examples.

The pour point was determined by American Society for Testing Materials (hereinafter referred to as ASTM) procedure D 97-57.

Kinematic viscosity was determined by ASTM D 445- T 1960 procedure, using ASTM kinematic viscosity ther mometers which had been calibrated against National Bureau of Standards resistance thermometers.

ASTM slope Was determined from the curve plotted from viscosity data on ASTM viscosity-temperature chart D 341 over the temperaturerange 100 C. to 210 C.

The llash point was determined by ASTM D 92-57 procedure.

The autogenous ignition temperature was determined by ASTM D-2155, D-60T procedure.

Flammability at l300 F. was determined by visual observation of the behavior of the test material when introduced dropwise at the surface of molten aluminum which is maintained at 1300 F. If no burning resulted, a single spark was applied for a more stringent test of fire resistance.

Vapor pressure and thermal stability measurements were conducted by employing substantially the method described by E. S. Blake et al., I. Chem. Eng. Data 6 87 (1961), using the isoteniscope, constant temperature bath and vacuum handling system.

Owing to the excellent physical properties of the present nuclearly chlorine-substituted diarylalkanes, the invention provides improved hydraulic systems wherein said chlorine-substituted compounds are employed as the operative lluids. Such systems comprise a displaceable member and a displacing force which is transmitted to said member by means of said lluid, as shown in the schematic diagram of FIGURE 1 of the drawings. Here, a displacing force is applied to piston 1 and transmitted through the lluid 2 contained in cylinder 3 whence it travels through line 4 into cylinder 5 where it acts on the displaceable member 6. In such a system, actuation of a movable member by the presently provided lluid gives performance characteristics which are outstanding because of the physical properties of the fluid. While hydraulic systems will contain such elements as pumps, valves, cylinders land pistons, the ellicacy of the system necessarily depends upon the fluid, since the lluid must be one which can withstand pressure and remain lluid under the conditions of use. FIGURE 2 of the drawings is a schematic diagram which well illustrates the indispensable role of the lluid in cooperation with other components of a hydraulic system. Here the lluid is stored in reservoir 21, and is pumped therefrom by means of pump 22 and through the directional control valve 23 into either end of cylinder 24, where it acts on piston 25 `connected by shaft 26 to a motor (not shown) or other device which converts the hydraulic pressure applied to piston 25 into mechanical energy. Action of the fluid on piston 25 displaces the piston until it reaches the end of its travel. The piston may be caused to travel in either direction by -adjustment of the directional valve 23. Valve 23 provides for return of the fluid from the opposite side of the piston, back to reservoir 21. Relief valve 28 is provided to maintain a constant hydraulic pressure within the system. When a predetermined pressure is reached, the lluid Will llow back to reservoir 21 by functioning of said relief valve.

Owing to their very good lire-retardant properties, the chlorinated diarylalkanes are particularly useful in hydraulic pressure devices that `are employed under conditions wherein any leak or break in the hydraulic system could provide great danger from lire. The exceptionally low pour points of the lluids permit fabrication of pressure devices which are destined for use in extremely cold climates, and their very good vapor pressure characteristics and stability to heat allows use ofthe same devices in -hot environments. The viscosity characteristics and ASTM slopes of t-he fluids makes them of great utility for the transmission of power in a hydraulic system having a pump therein which supplies power for the system, e.g., in a fluid 4motor comprising a -constantor variabledischarge piston pump which is caused to rotate by the pressure lof the hydraulic lluid of the system. The pre-sent lluid 4likewise serves to lubricate the frictional, moving part-s of such hydraulic systems.

For use in a conventional automatic transmission, the presently provided Ihydraulic lluid is contained in the outer casing of the transmission device, which casing is `attached to the usual engine crankshaft and flywheel and rotates therewith. Within the lluid is a coupling comprising an impeller connected to said casing `and a turbine which is connected to the drive shaft of the vehicle. The turbine is driven by the motion of the fluid in response to the rotation of the impeller, as the casing to which the impeller is attached is actuated by the crankshaft 1and flywheel.

The presently described nuclearly chlorine-substituted diphenylalkanes `are particularly suited for use as the operative llluids in hydraulic braking devices owing to their very good vapor pressure characteristics. Under current, severe operating conditions heat build-up within the brake system is frequently encountered. Unless the fluid remains liquid at the high temperatures thus developed, the hydraulic brake system becomes inoperable since t-he vaporized lluid becomes compressible. Although much ell`ort has been expended at providing high Iboiling hydraulic brake fluids, generally materials which are high boiling -congeal at low temperatures.

The presently provided lluids have boiling points which are well over 400 F. and some of them do not boil until over 600 F. Hence hydraulic brake systems in 8 which these lluids are-used withstand the dangers ensuing from heat build-up. At the 4same time, owing to the low pour points of the fluids, the system is one which is operable in very cold environment. The present invention fthus provides .an improved method for applying pressure to a hydraulic brake through -a fluid.

The presently provided compounds and mixtures are useful as the hydraulic lluids of hydraulic machines, generally, e.g., lifts, hoists, jack-s, lock-gates, presses, etc.

The invention is further illustrated by, but not limited to, the following examples.

EXAMPLE 1 Into a mixture consisting of 296 g. (1.0 mole) of 1,3- diphenylpropane Iand 4.2 g. of yanhydrous ferric chloride there was passed about g. of chlorine during a 20 minute period while maintaining the temperature of the reaction mixture at 27 C. by means of `an ice-bath. The resulting, purple lreaction mixture was diluted with an equal volume of benzene `and then washed lirst with dilute aqueous hydrochloric acid, then with dilute, aqueous potassium hydroxide and nally with water to neutrality. Distillation of the washed product -gave the following fractions:

(A) B.P. 192.5 C./l9 mm. to 196 C./17 mm., 88.2 g. (B) B P. 209 C.-218 C./17 mm., 43.8 g.

Analysis showed fraction (A) to contain 1 chlorine atom per molecule, and (B) to contain 2.2 atoms of chlorine per molecule. Nuclear magnetic resonance analysis for hydrogen proton showed an aromatic to aliphatic yarea ratio of 9,026.0 for cut (A) which agrees With 9.0:6.0, the theoretical value for nuclearly mono-chlorinated 1,3-diphenylpropane. For cut (B) the determined value was 7.8:6.0, which corresponds wel-1 to 8016.0, the theoretical value for a mixture of a nuclearly chlorinated diphenylpropanes having an average of 2.2 atoms of chlorine per molecule.

The pour point of the mono-chlorinated product, fraction A, was found to be 70 F. That of fraction B, having 2.2 atoms of chlorine was found to be -50 F. The yautogenous ignition temperature of (A) was determined to be 975 F. for 0.04 ml. with 87 seconds lag, .and that for (B) was found to be 1000 F. for 0.07 ml. with 63 seconds lag.

EXAMPLE 2 This example shows that to obtain a low pour point it is necessary, when the degree of nuclear chlorination is two, that the two phenyl groups be separated by an alk-ane structure. The presence of the phenyl groups on the same carbon atoms is disadvantageous.

Chlorine gas was passed into a vigorously stirred mixture consisting of 78.4 g. (0.4 mole) of 2,2-diphenylpropane and 2 g. of ferrie chloride over a period of 3 hours at a temperature of about 25 C. The Weight increase was 28.7 g. After diluting with benzene and washing to neutrality, first with dilute hydrochloric acid, then with aqueous sodium carbonate solution, the product was distilled to give a fraction B.P. 11S-118 C./0.06 mm., H1325 1.5885, analyzing an average of two Iatomsl of chlorine per molecule.

The fraction had a pour point of 5 F. The following kinematic viscosities were determined:

F.: Centistokes 25 7,110 27.21 210 2.97

The autogenous ignition temperature Was found to be 885 F. for 0.1 ml. With 39 seconds lag.

iEXAMPLE 3 Percent I Found I Caled. for 0101114.02013 The fraction thus contained a mixture of nuclearly chlorinated 1,4-diphenylbutanes having an average of about 4 chlorine atoms per molecule. It was found to have a pour -point of F. and the following kinematic viscosities `at the temperature shown below:

F.: Centistokes The ASTM slope was 0.93.

A flash -point of 469 F. was determined.

It did not burn when tested without spark in the molten metal test at 1300 F. and flashed with a single spark. An autogenous ignition temperature of 925 C. for 0.10 ml. with 20 seconds lag was determined.

EXAMPLE 4 Chlorine was bubbled into a stirred solution of 1,4- diphenylbutane (21 g., 0.1 mole) and anhydrous ferrie chloride (1 g.) in 100 ml. of carbon tetrachloride for 4.5 hours at 25 C. to 30 C. The total Weight increase at the end of this time was 8.4 g. The reaction mixture was `washed twice with dilute mineral acid, then with dilute caustic, and finally with water. After drying over magnesium sulfate it was distilled to give a fraction, B.P. 143-151 C./0.10 .15 mm., 111325 1.5734.. Nuclear magnetic resonance analysis indicated an average of about 2.4 aromatic chlorine atoms per molecule; and elemental analysis gave the following results:

Percent Found Calcd. for C1uHis.a2Cl2.3

C 66. 03 65. 73 H 5. 20 5. 34 Cl 29. 06 28. 92

Said fraction had a pour point of 40 F. (supercooled) 4and an autogenous -ignition temperature of 860 F. for 0.07 ml. with 28 seconds lag. The following kinematic viscosities were determined at the temperatures shown below:

F.: Centistokes The ASTM slope was I0.89.

EXAMPLE 5 0.15-0.17 mm., nD25 1.5629. By nuclear magnetic resol nance 'analysis it was determined that the fraction con- 10 tained 2 atoms of aromatic chlorine per molecule. Ele- Imental analysis gave the following results:

Percent Found a Calcd. for CnHlsClg The fraction was found to have a pour point of 50 F. and an autogenous ignition temperature of 875 F.

for 0.07 ml. with 25 seconds lag. The following kinematic viscosities were determined at the temperatures shown below:

F.: Centistokes The ASTM slope was 0.86.

Another batch of nuclearly dichlorinated 1,5-diphenylpentane prepared on a larger scale but by substantially the above procedure and having B.P. 149-l50 C./0.04 mm. was used in obtaining vapor pressure data and decomposition point. The temperatures for vapor pressure equal to certain pressures of mercury were determined to be as follows:

Temp. C.: Pressure, mm. Hg.

The decomposition point was 606 F.

EXAMPLE 6 Chlorine gas was bubbled into a mixture of 1,5-diphenylpentane (44.8 g., 0.2 mole) and anhydrous ferric Percent Found Calcd for Said fraction was determined to have a pour point of 5 F. and the-fol'lowingkinematic viscosities at the temperatures shown |below:

F.: Centistokes The ASTM slope Was 0.93. A flash point of 480 F. was determined. It had an autogenous ignition temperature of 880 F.

, for 0.04 ml. with 33 seconds lag. In the molten metal test at 1300 F. it `did not .burn in labsence of spark, and it flashed with .a single spark.

EXAMPLE 7 1,5-diphenyl-3methylpentanq B.P. 104 C./0\.04 mm., was prepared from B-methyl-LS-pentanedione by hydrogenation in benzene solution in presence of Raney Nickel and thiophene at a temperature of 220 C. anda maximum pressure of 2075 p.s.i. and subsequent distillation of the hydrogenation product. Nuclear .chlorination was effected by passing chlorine into a mix-ture consisting of 107 1g. (0.45 mole) of the 1,5-diphenyl-3-methylpentane and g. of Ifertric chloride in the fdark during a time of 3 hours while maintaining the temperature of the reaction mixture at 26-28 C. At the end of this time there was a 29 g. increase in the weight of the reaction mixture. It was taken up with benzene, washed with 20% aqueous hydrogen chloride, then with water, :subsequently with saturated aqueous sodium bicarbonate and finally with water to neutrality. After drying the organic phase over calcium sulfate, benzene was removed from the dried material, the residue was iltered .through clay and then distilled in vacuo to give the fraction B.P. 168 C./0.21, nD25 1.5582, analyzing for a mixture of nuclearly chlorinated 1,5-diphenyl-3-methylpentane having an average of 2.05 atoms of chlorine as follows:

Percent Found Calcd. for

CisHiessClms It was found to have a pour point of 35 F. The following kinematic viscosities were determined at The ASTM slope was 0.88. The autogenous ignition temperature was 875 F. for 0.04 ml. with 42 seconds lag.

EXAMPLE 8 1,5-diphenyl-3-methylpentane, B.P. 104 C./0.04 rnrn., which was prepared substantially as described in Example 7 was nuclearly chlorinated by passing chlorine into a mixture of 107 g. of the 1,5-diphenyl-3-methylpentane and 5 g. of ferric chloride during a 3-hour period while maintain-ing the temperature of the reaction mixture at from 25 to 28 C. A weight increase of 55.5 g. Wasthus obtained. The reaction mixture was then mixed with 500 ml. benzene and Ifiltered. After Washing the filtrate with 20% aqueous hydrochloric acid, water, saturated aqueous `sodium bicarbonate and finally with Water to neutrality, it was dried and filtered. Distillation of the filtrate gave the fraction A, B.P. 194 C./0'.21, 111325 1.5718 and the `fraction B, B.P. 207 C./0.20, 111325 1.5783.

By nuclear magnetic resonance analysis, raction A was found to contain no aliphatic chlorine. Elemental analysis showed the fraction to be a mixture having an ave-rage of 3.6 chlorine atoms per molecule, as follows:

Fraction B was also found to have no 'aliphatic halogen upon nuclear magnetic resonance analysis. Elemental analysis showed it to have an average of 4.3 atoms of chlorine per molecule, as follows:

Percent Found Calcd. for CISHUJCIM C 55. 92 55. 93 H 4. 71 4. 62 Cl 39. 75 39. 45

Fraction A was found to have an autogenous ignition temperature of 880 F. for 0.04 nil. with 52 seconds lag. In the 1300 F. molten metal bath test, in absence of spark, it -did not burn. In the presence of a single spark it flashed, but did not burn.

Like fraction A, fraction B did not burn in the absence of spark in the 1300' F. molten lignition test and flashed with a single spark. Fraction B had an autogenous ignition temperature of 910 F. folr 0.07 ml. with 25 seconds lag.

The kinematic viscosities of the two fractions were found to be as follows:

F. Centistokes Centistokes Fraction A had an ASTM slope of 0.94; that of B was 0.95.

Fraction A had a viscosity index of 135, and that of fraction B was -130.5.

EXAMPLE 9 Chlorine was allowed to pass into a mixture consisting of 49.7 g. (0.209 mole) of 1,6-diphenylhexane and 2.0 g. of ferric chloride for one hour in the dark and while maintaining the temperature of t-he reaction mixture at 4between 23 C. and 30 C. by means of an ice-bath. At the end of this time, the total weight increase was 15.2 g. The mixture was then diluted with 200 ml. of benzene, and the whole was Washed successive-ly with water, 6 N hydrochloric acid, saturated aqueous `sodium carbonate and iinally again with wa-ter. Theorganic phase was dried over calcium chloride and magnesium sulfate and filtered. Removal of benzene `from the filtrate gave a ydalrk oil which upon distillation in vacuum gave 23.9 g. of a mixture of [chlorine-substituted 1,6-diphenylhexane, B.P. l64-170 C./0.08-0.05 mm., showing a ratio of 12:7.5 `aromatic to aliphatic protons by nuclear magnetic resonance analysis. The mixture thus had an average of 2.5 chlorine atoms per molecule.

It was found to have a pour point of 40 F., and an autogenous ignition temperature of 865 C. for 0.04 ml. with 34 secon-ds lag.

In another :run, the above reaction was repeated, except that 21.1 g. (0.09 mole) of the 1,6-diphenylrhexane was used and the chlorine Igas was allowed to pass through the reaction mixture for 35 minutes. Upon Working up the product as above there was obtained a fraction, B.P. 13S-150 C./0.015 mm., 111325 1.5572, which analyzed an average of 2.2 atoms of chlorine per mole. It had a pour Ipoint of -45 F. and the following kinematic viscosities:

F.: Centistokes 25 10.48 5.2 2.7 210 0.78

Said fraction B.P. 13S-150 C./0.015 mm., had an autogenous ignition temperature of 850 F. for 0.04 ml. with 34 seconds lag.

In .still another run, 47.6 g. (0.2 mole) was chlorinated in presence of anhydrous ferric chloride for 5.4 hours at 25-29 C. to give a weight increase of 28.1 g. After working up as above, distillation gave a fraction B.P. 214-218 C./0.l6 mm., nD25 1.5742. Elemental and nuclear magnetic resonance -analysis showed the presence of an average of 4 chlorine atoms per molecule. It had a pour` point of *206 F. and the following kinematic viscosities:

F.: Centistokes 25 1,603 100 39.85 150 12 210. 4.63l

The autogenous ignition temperature was found to be 905 F. for 0.07 rnl. with 23 seconds lag. It Idid not burn in the molten metal testat 1300 F. in absence of spark.

The unch'lorinated 1,6-diphenylhexanehas a pour point A.

of -30 F. but it burns very readily at 1300 F.

Nuclearly brominated 1,6-diphenylhexane having an average -of 2 bromine atoms per molecule, is a solid which melts at about-60 C.

EXAMPLE 1o Chlorine was passed for 1.5 hours into a stirred mixture of 92.2 g. (0.35 mole) of 1,9-diphenylnonane and l g. of anhydrous ferric' chloride, during which time the temperature of the reaction mixture rose 6 C. A weight Percent Found Caled. for C21H24C14 The fraction is thus .a mixture of nuclearly chlorine-substituted 1,9-diphenylalkanes having an average of four chlorine atoms per molecule. It was found t-o have a pour point of -25 F. and the following kinematic viscosities.

F.: Centistokes It was `found to have an autogenous ignition temperature of 820 F. for 0.07 ml. with a 17 second lag.

In another run, operating substantially as above, chlorine was .passed into a mixture consisting of 70 g.. (0.4 mole) of 1,9-diphenylnonane `and 2.5 g. of anhydrous `ferric chloride to 4give a weight increase in the mixture of 32.5 lg. After working up the Ireaction mixture as above and =distilling, there was obtained a fraction B.P. 233- 235 C./0.12 mm., nD25 1.5629, which analyzed for an .average of 4.4 chlorine atoms per molecule, with nuclear magnetic resonance analysis .showing no aliphatic chlorine. This fraction had a pour point of 25 F. and

the following kinematic viscosities:

F.: Centistokes It had an autogenous i-gnition temperature of 285 F.

for 0.07 ml. with 20 seconds lag. When submitted to 14 ing to economic consider-ations, the operative iluid of the present hydraulic systems and methods may be any one chlorinesubstituted component of said mixture, provided the number of chlorine atoms present per molecule is at least one-third lof the number of aliphatic carbon atoms present. In some instances it will be found that those of such compounds having meta and/-or ortho-chlorine substituents poss-ess better iiuidity than do the para-substituted compounds. Hence, the choice of isomer may depend upon the environment in which the hydraulic pressure device is to be employed. I-f :such environment involves exposure of the dev-ice t-o very low temperatures, it will gen-` erally be desirable to use mixtures of isomers. Preparation lof such mixtures involves only routine procedures and is well within the skill ofthe art. Similarly, i desired, the mixture -of nuclearly-.substituted pro-ducts obtained .by reacting one diarylalkane with chlorine may be mixed with the nuclearly chlorinated products obtained from another diarylalkane. Such an expedient may be particularly advantageous when one of the` `diarylalka'nes is less readily available than the other, .for example, in the case yof the branched chain compounds. Also, it will be apparent that a Amixture of two or more diarylalkanes can be simultaneously chlorinated in the presence of an iron catalyst or of another catalyst known to be selective for aromatic substitution to give mix-tures of nuclearly chlorine-.substituted diarylalkanes whi-ch, if 4containing the proper ratio of chlorine to the aliphatic carbon, are eminently suited for use in hydraulic systems.

The nuclearly-chlorinated diphenylalkanes may also be mixed with known hydraulic fluids, eg., the trialkyl phosphates lor the dialkyl arylphosphonates, or with other fluids which are inert to the present chlorinated compounds, so long Ias the properties of the resulting mixture meet the speciiications required of a hydraulic fluid for the intended use. Obviously, if such use places no limitation on such -actors as either l-owor high-temperature behavior or if no tire-hazard exists, the present chlorine-substituted diarylalkanes may be present in any proportion. However, if one or more of these `fact-ors are important, then care sh-ould .be observed in preventing an undesired extent of dilution. Generally, lat least a major component of .the mixture should be nuclearly chlorinated 'diarylalkane Also, the usual fluid additives, e.-g., corrosion inhibitors, antioxidants, viscosity-index impr-overs, etc. may be Iadded to the present chlorinated diarylalkanes, although `for most purposes it will be found that such additives can be dispensed With.

It is to be understood that .although the invent-ion has been described with speciiic lreference to particular embodiments thereof, it is not to be so limited since changes and alterations therein may be made which are within the full intended s-oope of this invention as defined by the appended claims.

What we claim is:

1. A hydraulic pressure device, wherein -a displacing force is transmitted to a displaceable member by means of a hydraulic fluid, wherein the hydraulic fluid comprises a composition having a kinematic viscosity of 50 to 15,000 Centistokes at 25 E. and consisting essentially of a chlorine-substituted :diarylalkane of the formula Rm Z Cly

wherein Z is :an alkylene radical having ifrom 3 to 10 carbon .atoms in the chain which bridges the two benzene rings and a total of from -3 to -12 carbon atoms; R and R are alkyl radi-als of from 1 to 4 carbon atoms, the total number `of carbon .atoms in Z-i-Rm-l-Rn -is from I3 to 16, m and n are numbers of 0 to i3; y is a number oi from l to 5-m, z is a number of 0 to 5-n; and the sum of y-l-z is at least one-third lof 'but not more than the tot-al number oi aliphatic carbon atoms present in the molecule.

2. The' hydraulic pressure device described in claim 1,I

further limited in that eaeh of m .and n is zero.

3. The hydraulic pressure device as described in claim 1, further limited in that each of m and n is zero, Z is propylene and y+z=1 to 3.

4. The hydraulic pressure -device as desc-ribed in claim 1, further limited in that each -of m and n is zero, Z is butylene and y-iz=l.33 rto 4.

5. The hydraulic pressure device =as described in claim 1, further limited in that each yof m and n is zero, Z is pentylene and y-l-z=l.'66 to 5.

6. The hydraulic pressure device as described in claimA 1, further limited .in that each of m and n is zero, Z is 3-me-thylpentylene `and y+z=2 to 6.

7. The hydraulic pressure device :as described in claim 1, further limited in that each of m land n is zer-o, Z is hexylene and )I4-1:2 to 6.

8. The hydraulic pressure device as described in claim 1, further limited in that each of m and n is zer-o, Z is nonylene and y+z=3 to 9.

9. In the method :of operating -a hydraulic pressure device wherein a displacing force is .transmitted to a displaceable member -by means of .a hydraulic dluid, the improvement which comprises employing as theA hydraulic fluid a composition having a kinematic viscosity of 50 to 15 ,0100 centistokes at 25 F. and consisting essentially of 4a chlorine-.substituted diarylalka'ne of the formula Gly wherein Z is an alkylene radical having from 3 to l0 carbon atoms in the chain which bridges fthe two benzene rings Iand 4a total of from t3 to l2 carbon atcxms, R and R' are alkyl radicals of 'from 1 to 4 carbon atoms, the t-otal number of carbon atoms fin Z-l-Rm-l-Rn is from 3 to lr6,

` in .that each lof m and n is zero.

11. The method described in claim 9, fiurther limited in that each of m and n is zero, Z is propylene and y-l-z=1 to 3.

12. The method described in claim 9, further limited in that each fof m .and n is zero, Z is butylene and y-l-z=1.33 to 4.

13. The method described in Iclaim 9, further limited in that each Iof m and n Iis zero, Z is pehtylene and y+z=1.66 to 5.

.14. rIlhe method described in claim 9, further limited in that each yof m .and n is zero, Z is 3-methylpentylene and y+z=2 t-o 6.

15. The method described in claim 9, further limited in that cach of m yand n is zero, Z is hexylene and y-i-z=2 to 6.

16. The method described in claim 9, further limited in that each of m and n is zero, Z is nonylene and y+z=3 to 9.

References Cited by the Examiner UNITED STATES PATENTS 2,244,284 6/f1941 Britton et al. 260-649 2,600,691 l6/1'952 Ross et al. 260-649 2,623,910 12/1952 Robinson et al. 260-649 2,707,176 4/ 1955 Gamrath et al 252-78 SAMUEL H. BLECH, Primary Examiner.

ALBERT T. MEYERS, Examiner.

R. D. LOVERING, S. D. SCHWARTZ,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,290,253 December 6, 1966 Edward S. Blake et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as Corrected below.

Column l, line 24, for "opening" read operating line 25, for "htat" read that line 7l, after "l0" insert Carbon column 4, line 42, for "dimethy" read dimethyl Column 5, line 19, for "suihtable" read suitable column 9 line 3 after "with" insert dilute same column 9, in the second table, in the heading to the last column theTeOf, fOI "ClHlSZClZB" read Cl6Hl5.62ClZ 38 COlUmI l2, line 6l, for "l0.48" read 10.84 Column I3, line 67, for "285 F." read 825 F.

Signed and sealed this 16th day of July 1968. (SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

9. IN THE METHOD OF OPERATING A HYDRAULIC PRESSURE DEVICE WHEREIN A DISPLACING FORCE IS TRANSMITTED TO A DISPLACEABLE MEMBER BY MEANS OF A HYDRAULIC FLUID, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS THE HYDRAULIC FLUID A COMPOSITION HAVING A KINEMATIC VISCOSITY OF 50 TO 15,000 CENTISTOKES AT 25*F. AND CONSISTING ESSENTIALLY OF A CHLORINE-SUBSTITUTED DIARYLALKANE OF THE FORMULA 